Suspension Device for a Limb Prosthesis or Orthosis

ABSTRACT

A vacuum-assisted suspension device for a lower limb prosthesis secures the prosthesis to a residual body portion. Sandwiched between the residual body portion and an impermeable socket is a flexible liner made of an impermeable material that is porous to allow the transport of air and fluid directly away from the residual body portion to the outer surface of the liner. A fabric distribution layer is located over the liner and between the liner and the socket to allow transmission of such extracted air and fluid laterally over the liner to an evacuation port in the socket. The evacuation port has an associated one-way valve. During use, loading of the socket compresses the flexible liner and air is expelled via the evacuation port. When the load is removed, a vacuum is created directly between the residual body portion and the socket, the vacuum being maintained by the one-way valve.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of currently pending U.S. patent application Ser. No. 12/811,895 filed Jul. 7, 2010. The application claims priority from UK Patent Application No. 1021829.5 filed Dec. 21, 2010. The entire content of the '895 application is expressly incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a suspension device for a limb prosthesis, and to a suspension device for a limb orthosis. The invention is particularly applicable to a vacuum socket assembly for attaching a limb prosthesis to a residual limb portion. More particularly, the invention provides a new assembly and system for securing a prosthetic device to a residual lower limb portion for a transtibial amputee.

Maintaining an intimate fit between a residual body portion and the socket of a prosthetic limb is known to cause problems with the comfort and control of the limb prosthesis. It is known that these problems are, in part, due to the occurrence of relative movement between the residual body portion and the socket. Typically, this relative movement causes abrasions on the residual body portion and increased energy consumption during ambulation, as well as a lack of control of the prosthetic device.

It is known to improve amputee comfort by employing a liner made from a visco-elastic material, the liner being positioned between the residual body portion and the socket. Unfortunately, a typical liner does not breathe as it creates an airtight seal with the residual body portion in order to suspend the prosthetic device. Various methods have been devised to suspend the prosthetic device from a liner. For example, a pin attached directly to the distal surface of the liner may be fastened to the socket. Alternatively, suspension can be achieved using a flexible non-porous sleeve that is fitted externally so as to overlap the brim of the socket and to engage the wearer's skin above the socket brim thereby to create an air-tight seal.

Although the known methods can reduce relative movement of the residual body portion with respect to the prosthetic device thereby improving comfort for the amputee a further reduction is desirable.

Several innovations over recent years have sought to restrict relative movement between a residual body portion and a prosthesis further by applying an active vacuum via the liner to the residual body portion. An active vacuum is defined as one that is less than atmospheric pressure and is generated by, usually, either a mechanical or electrically powered vacuum pump. It is known to use such a vacuum pump in combination with a non-porous liner that effectively insulates and seals off air flow to the residual body portion. By ensuring an intimate fit of the liner to the residual body portion and evacuating the space between them using the vacuum pump, it is possible to secure the liner to the residual body portion purely by vacuum while minimising relative movement between the residual body portion and the liner. It is then possible to secure the liner to the socket of a prosthetic device. The Otto Bock Harmony® system is an example using this technique.

Another known liner system is the Iceross® Seal-In liner which is configured such that a vacuum is created when the residual body portion, covered by the liner, is pushed into the socket.

One difficulty encountered with all liners made of materials such as silicone is that, in a hot environment or during exertion, sweating results. This tends to increase relative movement between the residual body portion and the liner and, hence, the prosthetic device. Additionally, sweating creates a moist environment which softens the skin and provides a breeding ground for pathogens. The consequences of this are that the residual body portion is more prone to abrasion, tissue breakdown and infection. Ideally, relative motion between the skin and the socket interface should be eliminated.

It is known from WO 2007/030609 (King) to provide an inner fabric layer to act as a wicking layer between the tissue of the residual body portion and the liner. This fabric layer allows an active vacuum to propagate around the surface of the residual body portion and thereby assists in securing the liner and prosthetic device to the residual body portion. Furthermore, this wicking layer promotes the removal of fluid, i.e. sweat, from the surface of the residual body portion. Nevertheless, the potential for harbouring bacteria remains. In addition, the fabric layer can cause abrasion and damage of the tissue of the residual body portion with any relative movement.

U.S. Pat. No. 6,544,292 (Laghi) discloses a soft gel liner with a fabric-covered exterior.

EP 0182412A (Jongenengel) discloses a leather artificial limb socket having a thin flexible leather inner layer and a leather outer layer, the leather layers sandwiching therebetween a resilient thermoplastics layer bonded to the inner leather layer and having perforations which aid in the dissipation of heat and moisture from the residual limb enclosed by the socket.

U.S. 2001/0016781A (Capsers) discloses an example of a vacuum-assisted suspension socket having a flexible suspension sleeve overlapping the brim of the socket. Inside the socket, a sealed cavity is formed between the socket and a liner which is coextensive with the socket. Inside the liner is an osmotic membrane encasing the residual limb portion and, between the liner and the socket, there is a sheath of knitted nylon to aid fitting of the socket over the liner.

It is an object of this invention to provide an improved vacuum-assisted liner system and suspension device.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, a suspension device for a lower limb prosthesis comprises an air-impermeable socket shaped to receive a residual limb portion, the socket having an inner surface and an outer surface, a distal end and a proximal end, the proximal end being open and surrounded by a peripheral socket edge, a flexible liner shaped and dimensioned to be located between the inner surface of the socket and the residual limb portion when the socket is fitted to the residual limb portion, wherein the liner has an inner surface and an outer surface and at least a part of the liner is porous so as to allow transmission of air and moisture between the inner and the outer surface thereof, and a sealing member at the peripheral socket edge to form a seal between the socket and the residual limb portion when the socket is fitted to the residual limb portion, and wherein the socket has an evacuation port in communication with the evacuation port, which valve is oriented so as to maintain a vacuum generated inside the socket. The liner can be shaped and dimensioned to extend over the whole of the inner surface of the socket or it may extend only over a distal end portion of the socket against the inner surface. It is preferably formed from an air-impermeable material with perforations therethrough between the liner inner and outer surfaces to form the porous liner part. A distribution layer on an outer surface of the liner preferably allows transmission of air and moisture transversely from the perforations to the evacuation port. The distribution layer is preferably a fabric layer overlying the impermeable material of the liner on the outer surface thereof.

It is preferred that the perforations through the impermeable material of the liner have a diameter of less than 2 mm at the inner surface of the liner. It is more preferred that the diameter of the perforations is less than 1 mm at the inner surface.

In the preferred embodiment of the invention, the liner is made of a resilient elastomeric material such as a silicone material.

According to another aspect of the invention, a vacuum-assisted suspension device for a limb prosthesis or orthosis comprises: an air-impermeable outer wall member shaped to receive a residual limb portion, the wall member having a peripheral edge, an evacuation port, and a non-return valve associated with the evacuation port and arranged to maintain a vacuum between the wall member and the limb portion when the latter is received by the wall member; a resilient cushioning layer shaped and dimensioned to be located between an inner surface of the wall member and the limb portion, the cushioning layer having an inner surface and an outer surface; a porous distribution layer located between an inner surface of the wall member and the limb portion when the latter is received by the wall member, and adapted to allow transmission of air and moisture transversely through the distribution layer, the distribution layer extending over the outer surface of the cushioning layer and having a part which is in registry with the evacuation port; and means for forming a seal between the wall member and the limb portion in the region of the said peripheral edge; wherein the cushioning layer is made of an air-impermeable material at least part of which has perforations which extend through the layer from the inner surface to the outer surface thereof, the arrangement of the device being such that the corresponding apertures presented to the residual limb portion have a diameter of less than 2 mm at the inner surface of the cushioning layer.

In use of such a suspension device, it is possible for an active vacuum to be produced on the inside of the wall member, the vacuum acting both on the human body portion and the wall member. The vacuum creates a force to suspend the device from a human body portion whilst also minimising the relative movement between them.

The active vacuum is formed by compression and decompression of the flexible liner or resilient cushioning layer during locomotion. When the device is worn by a user, air and moisture are evacuated from within the device through the evacuation port and prevented from re-entering the device by the non-return valve. Mechanical work by the user forces the device towards the limb portion. This force works to compress the resilient cushioning layer, thereby increasing the pressure of the air contained within the device. The pressurised air is expelled from the device through the evacuation port. Once the loading force acting on the resilient cushioning layer is removed, the then unloaded resilient cushioning layer expands. The expansion of the cushioning layer provides a force acting on both the limb portion and the wall member. This force maintains a vacuum within the device even when no net force is acting between the limb portion and the device.

The resilient cushioning layer has a plurality of perforations to allow air (and moisture) to pass through the cushioning layer, away from the limb portion. The perforations preferably have a diameter (or equivalent transverse extent) of less 1 mm at the surface of the cushioning layer nearest to the limb portion. The maximum diameter of the perforations is set to minimise the risk of blistering the skin of the limb portion as a result of the vacuum transmitted through the perforations. If there is a fabric layer adjacent the inner surface of the cushioning layer, the diameter of the perforations at the inner surface may be greater than 1 mm.

The cushioning layer may be a liner shaped to extend over the residual limb portion to an edge in the region of the all member peripheral edge or a limb of limited area, i.e. in the form of a pad, preferably a distal pad. The perforations are preferably evenly distributed across an area of the liner. Alternatively the perforations may be formed in one or more groups with each group having a plurality of perforations. The perforations may be formed using laser beams to melt or ablate the resilient material. A resilient porous layer, with very small pores, i.e. smaller than 0.25 mm in diameter, may also be used.

The distribution layer is typically a synthetic fibre weave extending at least over the interface between the cushioning layer and the wall member.

The resilient cushioning layer may be manufactured from a silicone elastomer or a thermosetting gel material such as butyl-styrene. Materials other than the above may be used, especially those with similar physical properties. For instance, a sintered or porous resilient material may be used. Another alternative is a multiple-layer structure for the cushioning layer, having a sintered internal layer sandwiched between perforated layers formed of an impermeable material.

At least some of the perforations of the cushioning layer may have a cross-sectional area which varies along the length of the respective perforation, the diameter of each such perforation preferably being greater at the outer surface of the cushioning layer than at the inner surface thereof. If the cross-sectional area of a section of such a perforation increases as the distance from the residual limb portion contained within the suspension device increases, the velocity of a fluid travelling through the perforation away from the limb portion increases. This effect of the shaped perforations increases efficiency of the cushioning layer in transporting moisture away from the limb portion within the suspension device and inhibiting passage back through the perforations towards the limb portion.

The wall member may be shaped as a hollow elongate socket to receive an elongate residual limb portion, the socket having a proximal open end defined by its peripheral edge, and a distal closed end. The cushioning layer is preferably located at the distal closed end of the socket to maximise the pumping effect of the residual limb portion moving longitudinally within the elongate socket, and is shaped and arranged such that its inner surface abuts the residual limb portion over the whole of that inner surface.

The vacuum-assisted suspension device may having a cushioning layer as a single liner or pad, or it may have plural cushioning pads spaced apart from each other and located between the inner surface of the wall member and the distribution layer. The pad or pads may themselves have multiple layers. Beneficially, one pad may be located at the distal end of the socket and another adjacent to the peripheral edge of the wall member. The second cushioning pad adds to the pumping effect produced by the pad at the distal end of the socket. Further, if a second cushioning pad is orientated within the socket substantially in a different plane to that of a first cushioning pad, movement of the residual limb portion movement of the residual limb portion generally parallel to one of the cushioning pads tends to compress the other. A second cushioning pad may, therefore, provide a more efficient pumping effect within a suspension device compared to a single cushioning pad.

The comfort to the user of the suspension device and magnitude of the vacuum achieved within the suspension device is affected by the material of the cushioning layer. Resilience is the property of a material to absorb energy when it is deformed elastically and then, upon unloading, to have this energy recovered.

One measure of resilience is its durometer. Silicone rubber, for instance, typically has a shore durometer of between 20 and 55 (shore 00). Perforating the material of the cushioning layer reduces the durometer and modulus of rigidity. The material is chosen to have a durometer which suits the activity for which the prosthesis or orthosis is designed. Thus, running produces greater loads than walking and requires a material of higher durometer. Generally, the cushioning layer material, including perforations, has an effective modulus of rigidity in the region of the perforations such that it is capable of being compressed by the pressures produced between the wall member and the limb portion during the gait cycle.

From a method aspect, the invention also includes a method of suspending a lower limb prosthesis from a residual limb portion of an amputee, wherein the method comprises the steps of: providing a socket member made of an impermeable material and shaped and dimensioned to receive the lower limb portion, the socket having an evacuation port and a non-return valve which is in communication with the port and is oriented so as to allow air to flow from the inner surface of the socket to the outside but to prevent flow in the opposite direction, providing a flexible liner shaped and dimensioned to be located between an inner surface of the socket and the residual limb portion, at least part of the liner being porous so as to allow transmission of air and moisture between inner and outer surfaces of the liner, fitting the socket member, with the lower limb prosthesis attached thereto, to the residual limb portion with the liner sandwiched between the socket member and the residual limb portion, forming a seal between a peripheral edge of the socket member and the residual limb portion, applying the amputee's weight to the prosthesis via the residual limb portion to load the socket thereby to compress the porous part of the liner and evacuate air through the evacuation port from between the residual limb portion and the socket member inner surface, and removing the amputee's weight so as to unload the socket, the vacuum thereby generated between the residual limb portion and the socket inner wall being maintained by the non-return valve.

Described hereinafter is a vacuum-assisted liner system for use in a suspension device which is to be attached to a human body portion forming part of or associated with a limb. The system comprises a flexible liner to be fitted over the body portion and having at least one peripheral edge, the liner being made of a material impermeable to air and having a porous section spaced from the or each peripheral edge to allow transmission of air and moisture between an outer surface and an inner surface of the liner. A porous distribution layer overlies the outer surface of the liner and is adapted to allow transmission of air and moisture transversely over the said outer surface through the layer. Using such a liner system, it is possible, when an outer suspension device wall member, e.g. a socket, is fitted over the liner system, to create a vacuum directly between the residual body portion and the socket thereby to suspend a prosthetic device from the residual body portion whilst minimising the potential for relative movement between them. The vacuum is transmitted to the residual body portion through the porous section of the liner, the majority of the space between the liner and the socket being occupied by the distribution layer so that the vacuum created by evacuating the socket is transmitted over most of the area of the liner causing the liner to adhere to the inside of the socket over a wide area. The distribution layer allows air and fluid to be efficiently removed from the porous section of the liner.

The liner porous section may be made by forming a large number of perforations in the impermeable material of the liner, the perforations passing through the liner from its outer surface to its inner surface. Alternatively, the liner may be made of two materials, the porous section being made of a porous material which is joined to the impermeable material of the remainder of the liner. There may be more than one porous section.

In a particularly preferred embodiment of the invention, the liner is in the form of a hollow container dimensioned to fit over the residual limb portion, especially a below-knee residual limb portion of a transtibial amputee. The porous section or sections of the liner forms the distal portion of the liner. However, it is also possible, within the scope of the invention, to form the liner as a sleeve with proximal and distal open ends for the purpose of attaching an orthosis to a limb. In another embodiment of the invention, the liner is in the form of a cup or a dished patch for application to, for instance, the residuum of a through-hip amputee. In each case, the liner system is intended for use with an outer component in the form of the wall member to which a prosthesis or orthosis is attached, the wall member covering the porous section or sections of the liner and overlapping a peripheral edge or edges of the distribution layer to form a seal against the outer surface of the liner adjacent its peripheral edge or edges. In this way, when air is evacuated through a port in the wall member, the wall member is drawn onto the liner and, by virtue of the transmission of reduced pressure through the porous section, the liner is, itself, drawn onto the residuum, the space between the wall member and the liner being evacuated over the whole area of the distribution layer, the peripheral edge or edges of which are located to leave an exposed peripheral sealing portion or portions of the liner outer surface. The distribution layer extends over the whole of the liner porous section and beyond the boundary or boundaries of the porous section.

In the case of a liner system for enclosing a residual limb portion, the porous section or sections of the liner form a distal portion or portions thereof, extending from a distal end of the liner to an annular porous section boundary such that at least the distal third of the liner is porous (calculated as a fraction of the average length of the liner from its distal end to the rim. It is also possible for the extreme distal end to be impermeable and non-porous but for the major part of the liner distal portion to be porous.

Although the preferred material of the liner is a silicone material, it may also be a urethane-based material, or a gel such as tetrabutylstyrene gel.

The distribution layer is typically a synthetic fibre weave which may be integrated in the outer surface of the liner.

According to another aspect of the invention, a vacuum-assisted suspension device for a limb prosthesis or orthosis comprises: an air-impermeable outer component shaped to receive a human body portion; a flexible inner liner to be fitted over the body portion and having at least one peripheral edge, the liner being made of a material impermeable to air but having a porous section spaced from the or each peripheral edge to allow transmission of air and moisture between an outer surface and an inner surface of the liner; and a porous distribution layer sandwiched between the material of the liner and an inner surface of the outer component and adapted to allow transmission of air and moisture transversely over the said outer surface of the liner; the outer component having at least one air evacuation port to allow evacuation of air from the distribution layer. As stated above, the distribution layer typically extends over and beyond the porous section of the liner but is spaced from the or each peripheral edge of the liner to expose a border region of the liner outer surface. The component, typically in the form of a rigid outer wall member preferably covers the whole of the distribution layer and extends beyond the latter to engage the exposed outer surface between a peripheral edge of the distribution layer and the or each peripheral edge of the liner so as to form a substantially airtight seal against the liner.

In the case of the outer wall member being a hollow socket for receiving a residual limb portion, the inner liner comprises a hollow container with an open proximal end and a proximal closed distal end, the porous section of the liner comprising a distal portion thereof, with the distribution layer comprising a fabric sock between the outer surface of the liner and the inner surface of the socket. The port, in this case, is preferably in the form of a pipe union in a distal end portion of the socket, and may incorporate a non-return valve oriented to maintain a vacuum inside the socket once air has been evacuated.

According to yet another aspect of the invention there is provided a vacuum-assisted suspension device for a limb prosthesis or orthosis comprising a hollow air-impermeable outer container shaped to receive a human limb portion; a flexible inner liner to be fitted over the body portion and having at least one peripheral edge, the liner being made of a material impermeable to air; and a porous distribution layer between the material of the liner and an inner surface of the wall member and adapted to allow transmission of air transversely over an outer surface of the liner; the container having at least one air evacuation port to allow evacuation of air from the distribution layer; wherein the distribution layer has at least one peripheral edge, the or each such edge being spaced from the peripheral edge or edges of the liner to leave at least one outer sealing portion on the liner outer surface, and wherein the container is shaped and sized so as to cover the distribution layer and to extend beyond the latter to engage and seal against the outer surface of the liner between the peripheral edge or edges of the distribution layer and the peripheral edge or edges of the liner when air is evacuated from between the container and the liner via the evacuation port thereby to suspend the container on the liner.

It is a primary advantage of liner systems described in this specification that sweat is drawn away from the surface of the body portion to which it is applied, helping to maintain a drier interface with the liner. This can reduce the relative movement between the body portion and the wall member which improves an amputee's proprioception, and helps to avoid the other above-mentioned disadvantages of a moist environment. Relative movement is also reduced by arranging for a vacuum to be established directly between the tissue surface of the body portion and the surface of the wall member or socket. This, in turn, reduces the chance of the wall member abrading the skin of the body portion.

Summarising, in a preferred embodiment of the invention, for use with a lower limb prosthesis, the liner comprises a sock of impermeable material having perforations formed therethrough to allow transmission of a vacuum and fluid through the liner between an outer surface and an inner surface of the liner. A proximal part of the liner is non-porous in order to provide an air-tight peripheral seal around the residual body portion at a proximal end of the liner when air is evacuated from the socket. In another embodiment, that part of the sock having perforations formed therethrough is replaced by a section of air-permeable and fluid permeable material. In either case the liner wall thickness, at least in a distal part thereof, is at least 2 mm. In another embodiment a part of the distal part of the liner that would otherwise be porous is left non-porous to prevent vacuum being applied directly to hypersensitive tissue or to prevent the extraction of fluid from sensitive or adherent parts of the surface of the residual body portion.

According to a further aspect of the invention, there is provided a suspension device a for a limb prosthesis or orthosis, comprising: a hollow air-impermeable outer wall member shaped to receive a human limb portion; and a flexible inner liner to be fitted over the body portion and having at least one peripheral edge, the liner being made of a material impermeable to air but having at least one porous section spaced from the or each peripheral edge to allow transmission of air and moisture between an outer surface and an inner surface of the liner; the wall member having at least one air evacuation port to allow evacuation of air from between an inner surface of the wall member and an outer surface of the liner; wherein the wall member is shaped and sized so as to cover the porous section of the liner and to extend beyond the latter to engage and seal against the outer surface of the liner between the porous section thereof and the peripheral edge or edges of the liner to form, in use, a sealed enclosure between the wall member and the body portion, the enclosure including the liner porous section, such that when air is evacuated from the sealed enclosure via the evacuation port, the wall member is secured to the liner.

The invention will be described below by way of example with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a partly-sectioned schematic view of a preferred vacuum suspension device in accordance with the invention, shown mounted to a lower limb residuum;

FIG. 1A is a detail as indicated by the arrow A in FIG. 1;

FIG. 1B is a detail as indicated by the arrow B in FIG. 1;

FIG. 2 is a partly-sectioned schematic view of an alternative vacuum suspension device in accordance with the invention, shown mounted to a lower limb residuum;

FIG. 2A is a detail as indicated by the arrow C in FIG. 2;

FIG. 3 is a partly-sectioned schematic view of a third vacuum suspension device in accordance with the invention, shown mounted to a lower limb residuum;

FIG. 3A is a detail as indicated by the arrow D in FIG. 3;

FIG. 4 is a partly-sectioned schematic view of a fourth vacuum suspension device in accordance with the invention, shown mounted to a lower limb residuum;

FIG. 5 is a partly-sectioned schematic view of a fifth vacuum suspension device in accordance with the invention, shown mounted to a lower limb residuum;

FIG. 5A is a detail as indicated by the arrow E in FIG. 5;

FIGS. 6A and 6B are, respectively, a perspective view of a sixth vacuum suspension device in accordance with the invention, intended for mounting to a hip disarticulation residuum, and a sectioned schematic view of the sixth suspension device, shown mounted to the hip disarticulation residuum;

FIG. 7A is a partly-sectioned schematic view of a preferred vacuum-suspension device in accordance with the invention, shown mounted on a lower limb residuum;

FIGS. 7B and 7C are details from FIG. 7A;

FIG. 8A is a cross-sectional view of part of a cushioning layer having perforations of a first shape;

FIG. 8B is a cross-sectional view of part of a cushioning layer having perforations of a second shape;

FIG. 8C is a cross-sectional view of part of a cushioning layer having perforations of a third shape;

FIG. 8D is a cross-sectional view of part of a cushioning layer having a plurality of voids, some of which constitute perforations; and

FIG. 9 is a partly-sectioned schematic view of an alternative vacuum-suspension device in accordance with the invention, shown mounted in a lower limb residuum.

Embodiments of the invention described herein each comprise a liner system which includes a shaped liner for intimate fitting over a body portion such as the stump of an amputated limb from which a limb prosthesis is to be suspended or such as a complete natural limb to which an orthosis is to be attached. The liner is made at least partly of a flexible air-impermeable material. However, a section of the liner spaced from its edge or edges is porous to allow transmission of a vacuum through the liner between an outer surface and an inner surface of the liner. Additionally, an outer surface of at least the porous section of the liner is directly covered by a porous distribution layer for transmitting air and fluid transversely over the outer surface of the liner. When the liner has been fitted to the body portion referred to above, with the distribution layer on its outer surface, a substantially rigid cup, sleeve, or socket, depending on the shape of the body portion in question, is applied over the liner and distribution layer to form a vacuum-assisted suspension device as will be described below. In the case of the body portion being the residual limb of an amputee, the component applied to the liner system is a hollow socket. The residual body portion, when fitted with the liner system, is inserted inside the socket which then forms part of a prosthetic device replacing the amputated limb portion.

Whether it is in the form of a socket, sleeve, cup or disc, the component which is secured to the above body portion over the liner system is in the form of a substantially rigid wall member. This wall member has an inner receiving surface sized and shaped to abut the outer surface of part of the body portion with the liner placed over. A port is formed in the wall member to allow evacuation of air and fluid from the space between it and the liner. A non-return valve permits the evacuation of air and fluid via the port and can be used to maintain a vacuum between the wall member and the body portion. The valve may be incorporated in an evacuation pipe for connection to a vacuum pump.

An active vacuum region is created directly between the wall member and the tissue of the body portion adjacent the porous section of the liner, air being withdrawn via the port using the pump. The remainder of the liner is air-impermeable and forms a boundary of the evacuated region by creating a peripheral seal both between the liner and the body portion and between the liner and the wall member. The porous section of the liner allows transmission of air and fluid, for example, sweat, through the liner from the tissue of the body portion beneath the inner surface of the wall member. The porous distribution layer that covers the outer surface of the porous section of the liner allows transmission of the air and fluid between the outer surface of the liner and the inner surface of the wall member, and transversely and directly over the liner outer surface so that air is extracted from beneath the liner porous section to bring the skin of the body portion and the liner together, the extracted air being drawn to the port in the wall member via the distribution layer. At the same time, the liner and distribution layer are drawn against the inner surface of the wall member.

Referring to FIG. 1, a first liner system in accordance with the invention is for attaching a lower limb prosthesis to a lower limb residuum or stump 2. The liner system has a hollow liner 4 with a closed end and an open end which liner, in use, is fitted directly around the stump 2. As seen more particularly in FIG. 1A, applied directly to the outer surface of the liner 4 is a porous distribution layer 6 made of fabric or other air-permeable material allowing transmission of air transversely over the surface of the liner when the stump 2, fitted with the liner 4 and the distribution layer 6, is housed in a socket 8 of the lower limb prosthesis. The porous layer may be attached to the liner 4, integral with the liner or placed separately over the liner. The socket 8 is sized to receive all three of the stump 2, the liner 4 and the distribution layer 6 on the liner 4.

A port 10 is formed in a distal end portion of the wall of the socket 8, adjacent an interface 14 with the remainder of the prosthesis (not shown). The port 10 transmits air and fluid from the socket 8 via the port 10 through an evacuation pipe 12 connected via a pipe union to the socket wall. In this example, the interface 14 is a conventional pyramid-shaped spigot secured to the extreme distal end of the socket 8.

In this embodiment the material of the liner 4 is non-porous and air-impermeable. Silicone is the preferred material, but a flexible urethane or a tetrabutylstyrene gel (or similar) can be used. The liner comprises a proximal portion 4P with an open end and a distal portion 4D with a closed end. Formed in the distal portion 4D is a multiplicity of perforations 18, rendering the distal portion air- and fluid-permeable. The perforations 18 are distributed over the distal portion and each perforation 18 extends between an inner surface 20 and an outer surface 22 of the liner distal portion 4D substantially perpendicularly to these surfaces. The combination of perpendicularly oriented perforations 18 confining air and fluid transmission from the corresponding parts of the stump outwardly away from the stump surface and then transversely over the outside of the liner 4 through the distribution layer 6 efficiently draws the stump surface and the liner together when a vacuum pump is operated to withdraw air through the port 10 in the socket wall. Sweat is drawn directly away from the stump, helping to maintain a relatively dry stump/liner interface and maintaining intimate stump/liner contact. The vacuum created in the fabric distribution layer 6 between the liner 4 and the socket 8 draws the liner and the stump against the inner surface of the socket. In this way, the mechanical connection between the stump 2 and the socket 8 is improved, leading to improved proprioception. The lack of an intermediate layer between the liner and the stump minimises relative movement of the stump and the liner, results in easier cleaning of the liner, and avoids potential discomfort due to creasing of a fabric layer. As a further consequence, abrasion of the stump is reduced since relative movement of the stump within the socket is reduced and softening of the skin due to humidity is reduced.

The socket 8 is conventional insofar as it is made of a thermoplastics material such as a nylon based thermoplastics which is rigid compared to the liner, albeit with some resilience.

As shown more particularly in FIG. 1B, when air is evacuated from the socket 8, the boundary region 28 between the porous distal portion 4D and the impermeable proximal portion 4P of the liner 4 defines an airtight seal around the periphery of the stump by virtue of the impermeable nature of the proximal portion 4P which encircles the stump 2 and the fabric distribution layer 6 extending only over the distal portion 4D of the liner 4. As a result, the vacuum, preferably an active vacuum, created by pumping air from the port 10 holds the liner 4 to the socket 8 to provide suspension of the socket 8 from the stump 2 together with the remainder of the lower limb prosthesis (not shown) attached to the socket.

Referring to FIG. 2 and FIG. 2A, an alternative liner system in accordance with the invention has a liner 4 the whole of which, rather than just a distal portion, is formed with perforations 18 extending between the inner and outer surfaces. In this embodiment, the porous distribution layer 6 covers the complete outer surface of the liner 4. The effect of this structure is that air and fluid is drawn from the whole of the enclosed residual body portion or stump 2, through the liner 4. As before, the distribution layer 6 allows a substantially uniform pressure drop over the perforated area of the liner 4.

In this embodiment, to achieve suspension of the prosthesis from the stump 2, the interior of the socket is sealed by an annular sleeve 40 positioned proximally around the stump 2 and overlapping the proximal peripheries of both the socket 8 and the liner 4. The sleeve 40 is made of an air-impermeable material, such as silicone or urethane. It is important that the sleeve 40 fits closely over the stump 2, the liner 4 and the socket 8 so that when the socket 8 is evacuated, an airtight seal is formed between the stump and the socket.

As discussed above with reference to the prior art, an amputee may suffer negative consequences as a result of fluid forming on the surface of the stump 2. There is a variety of reasons why fluid may form, for example, sweat may be produced as a result of an increase in ambient temperature or because of physical exertion. Additionally, other body fluids may be produced on the surface of the stump, for example, by a wound.

Removal of fluid, by suction from the port 10, via the liner perforations and the distribution layer reduces relative movement between the stump and the socket and, avoids the formation of a moist environment which would soften the skin and provide an ideal breeding ground for pathogens. This is advantageous as a moist environment would make the residual body portion more prone to abrasion, tissue breakdown and infection. Furthermore, in the case of some wounds, the removal of fluid from the surface of the stump promotes healing.

In a further alternative embodiment, as shown in FIG. 3 and FIG. 3A, the liner distal portion 4D is formed of an inherently porous material rather than an air impermeable material having multiple perforations. A fabric may be used as the porous material. An open cell foam or a felt having a smooth surface may also be used; however, it is best if the chosen material does not absorb fluids so as to avoid creating a breeding ground for pathogens. A Goretex®-like fabric having a very closely woven surface is suitable. Additionally, as the distal portion 4D is porous, it can transmit air and fluid from the surface of the stump 2 to the port 10 and transversely within the liner distal portion 4D itself. Therefore, no porous outer distribution layer is needed.

In a further variation, shown in FIG. 4, the distal portion 4D of the liner 4 is perforated but has a section 50 without perforations 18. Section 50 is, therefore, impermeable to air and fluid and can be used to protect a sensitive or adherent area of the stump. (This may be because the area is particularly bony or is otherwise unsuitable for being subject to an active vacuum, e.g. owing to hypersensitivity or a possibility of adherence.) The size, shape and location of the impermeable section 50 can be customised according to the sensitive or adherent area. However, the surface area of the remaining, porous part of the distal portion 4D is sufficient to create a vacuum over a large enough area to secure the liner 4 to the stump 2.

Referring to FIGS. 5 and 5A, the invention includes a novel suspension system which may be used when moisture removal from the stump 2 is considered to be inessential. In this embodiment, the liner 4 is made of a flexible impermeable material, but has no porous section, whether in the form of a section with perforations or a section of permeable material. As in previously described embodiments, the socket 8 is made of a substantially rigid thermoplastics or laminated material and is sized and shaped according to the size and shape of the stump 2. Sandwiched between the liner 4 and the socket 8 is a porous distribution layer 6 spaced from the peripheral edge of the brim 8B of the socket 8 so that the socket 8 and the liner 4 are in intimate sealing contact in a boundary region 4BR proximally of the distribution layer 6 and adjacent the brim 8B of the socket 8. The port 10 in the wall of the socket is in registry with the distribution layer (as in previously described embodiments) in order that air may be withdrawn efficiently from between the socket 8 and the liner 4 through the distribution layer 6. Such evacuation, and the intimate contact between the liner 4 and the stump 2 draws the socket 8 onto the combination of the liner and the stump so that the assembly acts as a suspension device for limb apparatus attached to the stump interface pyramid component 14. It will be noted that the peripheral edge 4E of the liner 4 is preferably exposed beyond the outer edge or brim 8B of the socket B.

The particular embodiments of the invention described above are applicable to suspension of a prosthesis for a below-knee (transtibial) amputee. However, it should be noted that the invention also encompasses a liner system and socket assembly for an above-knee prosthesis (transfemoral); and for an above- or below-elbow prosthesis. Moreover, embodiments of the invention may be used to secure a device at the site of a shoulder or hip, or other body site. Such an embodiment comprises a liner and a dish-shaped socket. Operation of this embodiment is equivalent to the embodiments described above with reference to FIGS. 1 to 5. The invention may be used in connection with the suspension of the limb prosthesis or orthosis from any body portion which is suitably sized and shaped for a sufficiently large vacuum area to be created to secure a suspension device.

For instance, referring to FIGS. 6A and 6B, a substantially rigid dish-shaped wall member or receptacle 64 may be secured to a residual body portion 62 resulting from a hip or shoulder disarticulation. A flexible liner 64, also dish-shaped, is applied directly to the body portion 62. As in previously described embodiments, the liner is made of an air-impermeable material and has a porous section 64S the periphery 64SP of which is spaced from the peripheral edge 64E of the liner 64 to leave a non-porous boundary region 64BR surrounding the porous section 64S. The receptacle 68 is sized such that its own peripheral edge 68P and the annular edge portions adjacent the peripheral edge 68P is in registry with the boundary region of the liner when the receptacle 68 is applied to the liner 64. As in previously described embodiments, there is a fabric distribution layer overlying the porous section 64S of the liner, the periphery of the distribution layer 66 being spaced inwardly from the peripheral edge of the receptacle 68 to allow intimate sealing contact of the receptacle 68 with the boundary region 64BR of the liner 64, as shown in FIG. 6B.

As before, the receptacle 68 has an evacuation port 10 in registry with the distribution layer 66 and the porous section 64S of the liner 64.

Evacuation of air through the port 10 evacuates the space between the receptacle 68 and the liner 64, air being conducted transversely within the space by the distribution layer 66. At the same time, air is withdrawn from between the liner 64 and the body portion 62 through the perforated area of the liner and, in this way, the receptacle 68 is secured to the body portion 62 so that it can act as a mounting component for limb apparatus in the form of a prosthetic limb. The perforations in the liner 64 and the distribution layer 66 assist in drawing moisture away from the body portion 62.

A similar suspension device may be used for an orthosis.

It is also possible to construct the receptacle as a tubular sleeve to suspend an orthosis which encircles a limb with a tubular distribution layer and tubular layer beneath.

Embodiments of the invention have been described above with reference to an active vacuum created by a vacuum pump connected to the evacuation pipe. The vacuum pump may be a battery-powered pump or a purely mechanical pump powered by movement of a prosthesis or orthosis. However, it is preferred that the vacuum is created without a vacuum pump by using a one-way valve connected to the evacuation pipe. The one-way valve is arranged to maintain a vacuum within the socket during a swing phase by allowing air and fluid to exit the socket but not enter the socket.

Referring to FIGS. 7A to 7C, a further vacuum-assisted suspension device in accordance with the invention is for attaching a lower limb prosthesis to a lower limb residuum or stump 2. The stump 2 is housed within a stump socket 8. Within the socket 8 there is a resilient cushioning layer in the form of a cushioning pad 104 (see detail B shown in FIG. 1B) and a porous distribution layer 106. The distribution layer 106 is sandwiched between the outer surface of the cushioning pad 104 and the wall of the socket 8. The extent of the distribution layer 106 is such that the entire outer surface of the cushioning pad 104 is covered by the distribution layer.

A suspension sleeve 40 fits around a peripheral edge 8P of the socket 8. The suspension sleeve creates an airtight seal between the socket 8 and the skin of the stump 2. The suspension sleeve 40 allows a vacuum to be maintained within the socket 8 when a stump 2 is present within the socket 8.

A port 10 is formed in a distal end portion of the wall of the socket 8, adjacent a connection interface 14 with the prosthesis beneath (not shown) and in registry with the cushioning pad 104. The position of the port 10 in the socket wall is also such that it is in registry with the distribution layer 106. The port 10 transmits air and fluid from the interior of the socket 8 via the port 10 through a non-return valve 20 in an evacuation pipe 12 connected via a pipe union to the socket wall. The valve 20 is oriented so as normally to prevent flow of air into the socket from the outside. In this example, the connection interface 14 is a conventional pyramid-shaped spigot secured to the extreme distal end of the socket 8.

The cushioning pad 104 is formed of a resilient elastomeric material which is, itself, air and water-impermeable in this instance. Formed in the cushioning pad 104 are a plurality of perforations 104P. These perforations extend through the pad 104 from the inner surface thereof next to the stump 2, to an outer surface next to the wall of the socket 8. The perforations 104P render the cushioning layer formed by the pad 104 permeable to air and liquid in its perforated area or areas.

It is not necessary for the cushioning pad 104 to be perforated over the whole of its area, although in the case of the pad being confined to the distal end portion of the suspension device, as shown in FIG. 7A, it is preferred that the whole area is perforated as shown.

On the inner surface of the pad 104 there is an air and fluid permeable fabric layer in the form of a sock 109 which extends beyond the periphery of the cushioning pad 104 over the whole of the inner surface of the socket 8, terminating in the proximal edge portion 109P adjacent the peripheral edge 8P of the socket 8.

The socket 8 is conventional insofar as it is made of a thermoplastics material such as a nylon based thermoplastics which is rigid compared to the pad 104, albeit with some resilience.

As shown in FIG. 8A, each perforation 104P of the cushioning layer 104 is formed as a void in the material of the cushioning layer 104, the void taking the shape of a truncated cone and extending from the outer surface 1040 of the cushioning layer 104 to the inner surface 1041 thereof. The perforation 104P is flared outwardly, i.e., owing to the generally conical shape, it has a larger diameter at the outer surface 1040 (adjacent the distribution layer 4, as shown in FIG. 7A) than its diameter at the inner surface 1041 (adjacent the sock 109 and the stump 2).

In use of the suspension device, with a prosthetic shin and foot attached to the socket 8 by means of the pyramidal spigot 14, the repeated application and removal of a compression force on the cushioning layer 104 inside the socket 8 as the wearer is walking or running initially expels air from the space between the wall of the socket 8 and the stump 2 through the port 10. Owing to the presence of the non-return valve 20 in the pipe section 12 connected to the port 10, this creates a vacuum between the socket 8 and the stump 2 to hold the socket firmly on the stump.

The distribution layer 106 between the pad 104 and the wall of the socket 8 allows transverse passage of air and moisture, i.e. across the outer surface of the pad 104, equalising the reduction in pressure across the entire surface area of the pad. In addition, the perforations 104P allow air to be evacuated from between the pad 104 and the skin of the stump 2, equalising the reduction in pressure on opposite sides of the pad 104.

As described above, the perforations 104P also serve to transport moisture away from the surface of the stump 2, the pumping action of the pad 104 and the non-return valve 20 serving to draw moisture through the perforations 104P and the distribution layer 106, to be evacuated via the port 10. In this way, not only is the socket retained in close proximity to the stump 2, but also the build-up of moisture on the stump is reduced.

The outward flaring of the perforations 104P increases the flow velocity of air and moisture through the pad 104, helping to prevent the return of fluid when the pressure differential across the pad 104 reverses during walking or running.

The socket 8 is conventional insofar as it is made of a thermoplastics material such as a nylon based thermoplastics which is rigid compared to the pad 104, albeit with some resilience.

Referring still to FIG. 8A, the cross-sectional area of each of the perforations 104P at the cushioning pad inner surface 1041 is such that, for a circular cross-section, the diameter is no more than 2 mm. In the absence of a sock 109, the maximum diameter of the perforations of the inner surface 1041 is 1 mm.

Alternative cushioning pad configurations are shown in FIGS. 8B, 8C and 8D. Referring to FIG. 8B, the perforations 104P may be parallel-sided, so that the cross-sectional area at the pad outer surface 1040 is the same as at the pad inner surface 1041. As a further alternative, the perforations 104P may have a larger cross-sectional area at an intermediate depth, i.e. in the body of the pad 104 between the inner and outer surfaces 1041, 1040, as shown in FIG. 8C.

It is not necessary for all of the voids to penetrate the full thickness of the pad 104. Accordingly, as shown in FIG. 8D, the pad 104 may have perforations 104P as well as voids 104V each having an opening on the outer pad surface 1040 but a blind end in the body of the pad. Such voids assist in evacuating air from between the socket 8 and the stump 2 when the pad 104 is repeatedly compressed. Blind voids 104V may be formed so as to open out on the inner surface 1041 as well as, or instead of, those opening out onto the outer surface 1040. In some circumstances, if moisture dispersal is not required, the cushioning pad may be formed without, or with very few, perforations 104P, air evacuation being performed entirely by means of blind voids such as those shown in 16V in FIG. 2D.

The perforations 104P and blind voids 104V may be formed in a number of ways: by using a laser to cut the perforations in a pre-formed cushioning layer, or by driving one or more rods into the preformed cushioning layer. Alternatively, they may be produced during the forming of the cushioning layer, e.g. by appropriately shaping a mould in which the cushioning layer is moulded.

Referring to FIG. 9, a second vacuum-assisted suspension device in accordance with the invention has a first, distal resilient cushioning pad 104 and a second lateral resilient cushioning suspension pad 105. The first pad 104 is positioned remotely from the peripheral edge 8P of the socket 8 at the distal end, while the second pad 105 is positioned adjacent the peripheral edge 8P of the socket 8. The first cushioning pad 104 acts to evacuate air from within the suspension device as a result of longitudinal motion of the stump 2 within the device, while the second cushioning pad 105 acts to evacuate air from within the suspension device as a result of transverse or rocking motion of the stump 2 within the device, or as a result of hydrostatic loading of the stump 2. It should be noted that the distribution layer 106, in this case, extends proximally to cover the entire outer surface of the lateral cushioning pad 105 and also connects that outer surface to the outer surface of the distal cushioning pad 104 to allow transmission of air and moisture from the region of the lateral pad 105 to the evacuation port 10.

In FIG. 9, the second cushioning pad 105 is positioned laterally. It is also possible to have the second cushioning pad positioned medially or anteriorly.

In an embodiment in which the resilient cushioning layer is in the form of a hollow, elongate internal socket lining which has a perforated distal region, as shown in FIG. 1, and the peripheral portion of the liner is not perforated and extends beyond the proximal periphery of the socket stump, the sealing sleeve 40 of the embodiments described above with reference to FIGS. 7A and 9 can be dispensed with. It is also possible to incorporate a second perforated area positioned laterally, medially or anteriorly in such a layer to assist with evacuation of the space between the socket and the stump providing a distribution layer extends over the outer surface of the cushioning layer in registry with each perforated area, and a path to the evacuation port is provided.

As yet a further alternative, a perforated resilient pad can be used in conjunction with a standard impermeable liner to aid in its retention. In addition, the pad can be formed as part of a multi-layered liner providing, again, a distribution layer is included as a means of transmitting air and moisture from the outside of the perforated section to an evacuation port, as in the above-described embodiments. 

1. A suspension device for a lower limb prosthesis comprising: an air-impermeable socket shaped to receive a residual limb portion, the socket having an inner surface and an outer surface, a distal end and a proximal end, the proximal end being open and surrounded by a peripheral socket edge, a flexible liner shaped and dimensioned to be located between the inner surface of the socket and the residual limb portion when the socket is fitted to the residual limb portion, wherein the liner has an inner surface and an outer surface and at least a part of the liner is porous so as to allow transmission of air and moisture between the inner and the outer surface thereof, and a sealing member at the peripheral socket edge to form a seal between the socket and the residual limb portion when the socket is fitted to the residual limb portion, and wherein the socket has an evacuation port in communication with the porous part of the liner and a non-return valve in communication with the evacuation port, which valve is oriented so as to maintain a vacuum generated inside the socket.
 2. A suspension device according to claim 1, wherein the liner is a pad adjacent the distal end of the socket.
 3. A suspension device according to claim 1, wherein the liner is formed of an impermeable material with perforations therethrough between the liner inner and outer surfaces to form said porous part.
 4. A suspension device according to claim 3, wherein the liner has a distribution layer on its outer surface to allow transmission of air and moisture transversely from the perforations to the evacuation port.
 5. A suspension device according to claim 4, wherein the distribution layer is a fabric layer overlying the impermeable material of the liner on the outer surface thereof.
 6. A suspension device according to claim 3, wherein the perforations have a diameter of less than 2 mm at the inner surface of the liner.
 7. A suspension device according to claim 6, wherein the perforations have a diameter of less than 1 mm at the liner inner surface.
 8. A suspension device according to claim 1, wherein the liner is made of a resilient elastomeric material.
 9. A suspension device according to claim 3, wherein the liner is made of a silicone material and has a thickness of at least 2 mm.
 10. A vacuum-assisted suspension device for a limb prosthesis or orthosis, comprising: an air-impermeable outer wall member shaped to receive a limb portion, the wall member having a peripheral edge, an evacuation port, and a non-return valve associated with the evacuation port and arranged to maintain a vacuum between the wall member and the limb portion when the latter is received by the wall member; a resilient cushioning layer shaped and dimensioned to be located between an inner surface of the wall member and the limb portion, the cushioning layer having an inner surface and an outer surface; a porous distribution layer located between an inner surface of the wall member and the limb portion when the latter is received by the wall member, and adapted to allow transmission of air and moisture transversely through the distribution layer, the distribution layer extending over the outer surface of the cushioning layer and having a part which is in registry with the evacuation port; and means for forming a seal between the wall member and the limb portion in the region of the said peripheral edge; wherein the cushioning layer is made of an air-impermeable material at least part of which has perforations which extend through the layer from the inner surface to the outer surface thereof and which have a diameter of less than 2 mm at the inner surface of the cushioning layer.
 11. A device according to claim 10, wherein the perforations have a diameter of less than 1 mm at the cushioning layer inner surface.
 12. A device according to claim 10, wherein at least some of the perforations are tapered, the diameter of each such perforation being greater at the outer surface of the cushioning layer than at the inner surface thereof.
 13. A device according to claim 10, wherein the cross-sectional area of each of at least some of the perforations varies along the length of the perforation.
 14. A device according to claim 10, wherein the wall member is an elongate socket shaped to receive a residual limb portion, the socket having a proximal open end defined by the peripheral edge and a distal closed end, and wherein the cushioning layer is located at least at the distal closed end of the socket.
 15. A device according to claim 14, wherein cushioning layer comprises first and second perforated cushioning pads, the first pad being located at the distal closed end of the socket and the second pad being located in registry with a side wall portion of the socket, and wherein the distribution layer extends over the outer surfaces of both cushioning pads.
 16. A device according to claim 15, wherein the second cushioning pad is located adjacent the peripheral edge of the wall member.
 17. A device according to claim 14, wherein the cushioning layer comprises at least two non-overlapping cushioning pads each having a plurality of said perforations, the distribution layer extending over both pads.
 18. A device according to claim 15, wherein the second cushioning pad is located so as to abut a medial surface or a lateral surface of the residual limb portion when the device is fitted thereto, whereby lateral movement of the residual limb portion within the device causes compression of the said second cushioning pad.
 19. A device according to claim 15, wherein the second cushioning pad is located so as to abut an anterior surface or a posterior surface of the residual limb portion when the device is fitted thereto, whereby movement of the residual limb portion in the anterior-posterior direction causes compression of the said second cushioning pad.
 20. A device according to claim 10, wherein the material of the cushioning layer has an effective modulus of rigidity in the region of the perforations such that it is capable of being compressed by the pressures produced between the wall member and the limb portion during the gait cycle.
 21. A device according to claim 10, wherein the material of the cushioning layer is a material with a durometer value of between 20 and 55 shore
 00. 22. A device according to claim 14, wherein the distribution layer extends over the entire inner surface of the socket.
 23. A device according to claim 10, including a porous inner fabric layer at least a part of which extends over the inner surface of the cushioning layer.
 24. A device according to claim 23, wherein the porous layer extends over and is in registry with the entire inner surface of the socket.
 25. A method of suspending a lower limb prosthesis from a residual limb portion of an amputee comprising: providing a socket member made of an impermeable material and shaped and dimensioned to receive the lower limb portion, the socket having an evacuation port and a non-return valve which is in communication with the port and is oriented so as to allow air to flow from the inner surface of the socket to the outside but to prevent flow in the opposite direction, providing a flexible liner shaped and dimensioned to be located between an inner surface of the socket and the residual limb portion, at least part of the liner being porous so as to allow transmission of air and moisture between inner and outer surfaces of the liner, fitting the socket member, with the lower limb prosthesis attached thereto, to the residual limb portion with the liner sandwiched between the socket member and the residual limb portion, forming a seal between a peripheral edge of the socket member and the residual limb portion, applying the amputee's weight to the prosthesis via the residual limb portion to load the socket thereby to compress the porous part of the liner and evacuate air through the evacuation port from between the residual limb portion and the socket member inner surface, and removing the amputee's weight so as to unload the socket, the vacuum thereby generated between the residual limb portion and the socket inner wall being maintained by the non-return valve.
 26. A suspension device for a lower limb prosthesis comprising: an air-impermeable socket shaped to receive a residual limb portion, the socket having an inner surface and an outer surface, a distal end and a proximal end, the proximal end being open and surrounded by a peripheral socket edge, a flexible liner shaped and dimensioned to be located between the inner surface of the socket and the residual limb portion when the socket is fitted to the residual limb portion, wherein the liner has an inner surface and an outer surface and is formed of a resilient air-impermeable material with voids which are open at least at the outer surface of the liner, and a sealing member at the peripheral socket edge to form a seal between the socket and the residual limb portion when the socket is fitted to the residual limb portion, and wherein the socket has an evacuation port in communication with said voids in the liner and a non-return valve in communication with the evacuation port, which valve is oriented so as to maintain a vacuum generated inside the socket.
 27. A suspension device according to claim 26, wherein at least one of the voids constitutes a perforation of the liner extending through the liner from the inner surface to the outer surface thereof. 